1. Field of the Invention
The invention is directed to a method for processing image data, in which at least one section of a form is scanned in a raster-like manner and converted into a digital image with picture elements. The color of each and every picture element is presented according to the HSB color presentation as hue H, saturation S and brightness B, and a gray scale value GW is allocated to the respective picture element. This type of method can be utilized everywhere that great quantities of forms are read in a raster-like format and the information contained in them are edited with optical character recognition for further electronic data processing. Forms generally have structuring aids, also called scatter information, that ensure that the information fetched by a user (“payload information”) are ordered in a specific way and applied on the form in a uniform fashion. It is necessary for dependable and fast text recognition to separate the scatter information from the payload information.
2. Description of the Related Art
In automatic document processing applications, for example, colors are selected for the scatter information that can be easily filtered out by optical filters. What is disadvantageous about the method is that only a few interconnected wavelength regions of the light can thus be filtered out.
Another known method is digital color filtering of the colors of the picture elements of a form read in raster-like. Many wavelength regions of the light, even those that are non-interconnected, can thus be filtered out. What is disadvantageous about this digital filtering process is that, fundamentally, the property of scatter or payload information must be assigned to every color occurring on the form so that a decision can be made as to whether a picture element having such a color carries payload or scatter information. Due to fluctuations in the illumination of the forms during read-in, however, color modifications occur and mixtures that often no longer allow an unambiguous allocation of the picture elements also occur within a form due to neighboring picture elements having different colors.
The document, Carron et al., “Fuzzy Color Edge Extraction by Inference Rules: Quantitative Study and Evaluation of Performance,” Proceedings of the International Conference on Image Processing (ICIP), US, Los Alamitos, IEEE Comp. Soc. Press, October 1995 (1995-10), pages 181-184, XP000623941 ISBN: 0-7803-3122-2, is viewed as the most relevant Prior Art with respect to the present invention. It discloses a method for processing image data, in which the color of each and every picture element is presented in the HSI color space.
According to a fuzzy technique, the membership of the pixels in the edge class is determined with color differences from the neighboring picture elements from different membership functions. The degree of the membership in the edge class is determined by a combined minimum and maximum formation.
U.S. Pat. No. 5,778,156 discloses a method for processing image data in which at least a section of a form is scanned raster-like and converted into a digital image with picture elements, by which the color of each and every picture element is presented. The memberships of the color of each and every picture element in three image classes is determined from different membership functions according to a fuzzy technique, and the respective picture element is further processed depending on the identified memberships.